You enter a room with two cages. One contains a friend, who is clearly distressed. The other contains a bar of chocolate, which clearly isn’t. What do you do? While a few people would probably go for the chocolate first (and you know who you are), most would choose to free the friend. And so, it seems, would a rat.

Inbal Ben-Ami Bartal from the University of Chicago found that rats will quickly learn to free a trapped cage-mate, even when they get nothing in return, or when there’s a tasty chocolate distraction around. Bartal thinks that the rats conduct their prison breaks because they empathise with one another. This ability to understand and share the feelings of another individual is found in humans, apes, elephants, dolphins and other intelligent animals. It seems that rats belong in this club too.

This is either a surprise or a retelling of old news, depending on how far back your memory goes. In 1959, the psychologist Russell Church trained a rat to press a lever for food. Then, he connected the lever to the electrified floor of a cage containing another rat. If the first rat pressed the lever, the second one would get a painful shock. That’s not what happened – when the first rat saw what was going on, it forfeited its food and avoided the lever.

Church’s published his results in a provocative paper called “Emotional reactions of rats to the pain of others”, which sparked a flurry of similar studies throughout the 1960s. But the time wasn’t right. Psychologists were mostly interested in what animals did rather than what they felt, and the dominant view of nature red in tooth and claw left little room for cuddly feelings of empathy or altruism. “No one knew what to do with the studies, and they were forgotten,” says Frans de Waal, who studies how animals think.

In later years, the taboo on animal empathy began to lift and people became happier to ascribe it to the wider animal kingdom. In 2006, Dale Langford from McGill University returned to Church’s work and produced more evidence that rats can feel empathy. She showed that mice become more sensitive to pain when they see their cagemates in it.

It seemed that rats are sensitive to each other’s emotions, ‘catching’ them from one another. But Bartal wanted to know if this “emotional contagion” would actually motivate rats to help one another. Would empathy lead to action? Arguably, Church showed as much back in 1959, but psychologists have wondered whether the rats stopped pressing the levers out of concern for their fellows, or out of fear that their own floors would be electrified. Bartal needed a new experiment.

She kept her rats in pairs for two weeks, and then placed one of them in a cage. The trapped rats were clearly stressed – Bartal used a bat detector to show that they were occasionally making high-pitched alarm calls. Their partners could free them by pushing against a restraining door and tipping it over. That’s what they did, although most took a week to learn how.

Bartal found that the rats spent more time exploring the cage, and were more likely to open it, when there was another rat inside. It didn’t matter if the liberated rat got nothing in return. When Bartal changed the set-up so the only exit from the cage led to a different arena, the free rat still opened the door for its colleague, who promptly scurried away.

Even when the rats were faced with a second cage containing delicious chocolate chips, they freed their cage-mate as often as they went for the food. They even shared their chocolate bounty with their liberated pals. “Empathy is a truly powerful motivator, on a par with the desire for chocolates!” says de Waal.

Stephanie Preston, who works on animal emotions, says that Bartal has strengthened the case made by the studies from the 50s and 60s. “As shown previously, the rodents were not only empathically aroused by the emotion of [another rat], they took direct action to help. This is the definition of empathy,” she says.

There are alternative explanations, but none of them are strong. They weren’t just trying to silence the grating alarm calls from their trapped peers, because such calls were too rare to be a potent motivator. They weren’t just curious about the trapped rat, because they still opened the cages if they were very familiar with the animal inside. And they weren’t just looking for something to do for the door mechanism is difficult. The only explanation that really fits the rodents’ actions is that they were trying to end the distress of the trapped rat, or perhaps their own distress at seeing their cage-mate’s plight.

“The study is truly ground-breaking,” adds de Waal. It shows that rodents are not just affected by the emotions of others, but that empathy motivates altruism. Instead of explaining altruism by a cost/benefit calculation, as biologists and economists like to do, we are now entering a distinctly psychological realm of emotions and reactions to the emotions of others. This is where most human altruism finds its motivation and where, as this study suggests, animal altruism does too. In fact, the cost/benefit analysis was carried out long ago by evolution.”

De Waal suggests that the rats’ behaviour is the result of ancient neural circuits that allow mammals to “make the situation of others their own to some degree, thus offering them an emotional stake in it.” These circuits underlie the behaviour of apes, dolphins, elephants, rats, and probably more. De Waal thinks that they originated from the care that mammal mothers offered towards their young, which might explain why female rats (like female chimps and female humans) seem to be more empathic than male ones. In Bartal’s experiment, all the female rats opened doors for a trapped individual, compared to just three-quarters of the males.

Maybe it’s not altruism, maybe rats can think. Maybe the rats are thinking that boy if that was me I’d sure want out. So I’ll help this guy/gal and when I need help maybe somebody will be there for me.
Selfish enough Jose?

What immediately springs to mind is if innate empathy is a ride-along effect in male rats, the frequency is the same as the similar putative case of orgasms in females, ~ 75 %. (I assume there are social confounds though, human males are empathic.)

@ jose:

At the gene level alleles can only be “selfish”, AFAIK. But genes are not species.

I was surprised to learn recently that rats are highly social; I didn’t know that. I would suggest a link between social behaviours and altruism. Creatures that are less social should also be less altruistic. This is of course a testable hypothesis.

I thought it was common knowledge how social rats are, which is another way they become “pests” by working together so well. They’re very sweet animals, they’ll take care of one another’s young as well.

I was originally confused by the use of “empathic” in the title. I have always used the word, “empathetic.” It turns out that “empathetic” is relatively new in the dictionary and was only deemed acceptable after so many people used the non-existing word incorrectly. Learn something new every day!

How related were the exterimental animals? Looking at the supplementary material, it seems there was no control for relatedness. These mice could still be preferably helping siblings or cousins (the authors controlled for age).
I posit that emotional empathy is likely be calibrated by kin selection.

I’ve had rats as pets, a total of 7 female rats over a 4 year period, starting with two amazingly intelligent and empathic store rats, followed by a series of ‘rescue’ rats from homes and two from labs. All were various shades of tan and brown, except for the albino lab rats.

My smartest rat easily had high dog-level intelligence, and after being trained to not chew electrical cords or furniture, and not to hoard food, was given full run-of-the-house privileges. She had a regular routine of ‘tucking me in’ at night, snuggling up to me from the time I turned off the lights until I fell asleep. When I caught a cold or flu, she’d continually check on me and spend lots of time grooming me.

All the rats shared a large cage on a table. Since only one rat had passed all my requirements for freedom, I trained her to be able to go to and from the cage at will, while training all the others to fear leaving the table on which the cage sat (mild aversion training, nothing traumatic).

The Sprague-Dawley lab rats (I forget the strain code) were only capable of minimal training, and also were minimally interactive or affectionate with me, though they were never hostile, and the other rats clearly loved them. The lab rats were also the shortest-lived, succumbing to respiratory infections at about 1 year of age.

The other rats lived longer, were better able to beat the respiratory infections, and lived long enough to get multiple mammary tumors (which are common in female rats) and survive surgery.

While all my rats did their best training while young, all but the lab rats continued to learn throughout their lives, though at diminishing rates. In particular, they became more social with me as time progressed. It was especially joyful for me when I came home from work to see them lined up on the edge of the table eager to greet me!

What was most amazing to me was their behavior when near death. When they became too weak for surgery and/or drugs failed to work, I would euthanize only those who were in obvious pain. While I could detect some of the pain on my own, such as while handling them, the clearest indication was the behavior of the other rats. A rat that was infirm but was in no pain would receive occasional grooming and food from the other rats. A rat in pain would be surrounded by the other rats, snuggled together.

I loved having rats as pets, but the frequent tiny deaths took their toll on me, and after the first 5 deaths I decided I would not replenish their population. When my last rat started to fail, I took time off work to be with her, holding her continually. I’m absolutely certain she sensed my melancholy mood, for she kept trying to groom me right up to the end, despite being tumor-ridden and blind herself.

The notion of rat empathy(and intelligence) is no secret to those of us who have shared our lives with them.